Calender loading mechanism



Oct. 15, 1968 E. E. cRlsT ETAL. 3,405,632

CALENDER LOADING MECHANISM Filed Sept. 5, 3,965

/V/ dA--zz- EDWARD .0. BECHLE? ATTORNEYS United States Patent O 3,405,632 CALENDER LOADING MECHANISM Elmer E. Crist and Edward D. Beachler, Beloit, Wis.,

assignors to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed Sept. 3, 1965, Ser. No. 485,057 6 Claims. (Cl. 100-41) ABSTRACT F THE DISCLOSURE A calender roll stack having roll bending means on the top and bottom roll and a means for applying upward forces to the bearings and rolls of the intermediate rolls for obtaining the same nip pressure for each nip of the calender and for obtaining uniform pressure along the nips.

The present invention relates to the portion of a paper machine known as the calender or calender stack, and more particularly to an improved multi-nip calender.

Although the invention may have utility in a number of fields involving the pressing, smoothing, ironing or like treatment of a strip of exible material, a specific preferred use is in the paper machine calender. The operation of the calender in a paper machine is well known and understood in the art. The purpose of the calender stack is to compact the paper to some extent and give it a ne smooth finish. The fact is obtained on both sides of the paper by use of friction and pressure. The calender stack comprises a plurality of conventionally upright or vertically aligned horizontally disposed calender rolls, which may be thought of lying in a generally vertical plane (Le. the generally vertical plane dened by the nips of the calender). Although calenders are known wherein the rolls are not stacked in exact vertical alignment and the principles of the instant invention are readily applied to such calender arrangements, the conventional calender arrangement and the one preferred for use in the practice,

of the instant invention does involve vertically stacked rolls and the invention will be described primarily in connection with this type of calender (although the rolls could be aligned in other non-vertical arrangements).

In the conventional vertically aligned calender stack, the lowest or bottom roll of the stack is driven mechanically and it, in turn, drives the roll immediately thereabove, and so on, by friction. There is a certain amount of work between these rolls and the result is that there is a substantial amount of work performed on the paper as it passes through each of the calender nips. The paper web is directed rst to the top roll of the stack and it passes either over the top roll and through the top nip or directly through the top nip from which it follows the next roll down to the next nip and is transferred thereon to the surface of the third roll and so on, until the web passes through the bottom nip between .the bottom or king roll and the roll immediately thereabove.

In the calendering or finishing of number of types of papers there is an optimum and/ or maximum nip pressure which lcan be tolerated by the paper. For example in newsprint paper there is a maximum permissible pressure above which the sheet will be damaged. Too high calender nip pressure will cause blackening of the sheet and crushing with consequent reducing of bulk. Because of this fact it has been conventional to load the calender nips so that this maximum tolerable nip pressure occurs in the lowermost nip of the stack. Each nip above the lower nip is operated at some lower pressure. In a typical calender stack arrangement each successive nip up ice wardly from the lower one has a lower nip pressure with the difference in pressure resulting from the weight of the calender roll above it.

Conventional calender stacks are provided with nip loading facility wherein a force is usually applied to the top roll of the calender stack. This force is increased until the lowermost nip reaches the maximum pressure which can be tolerated by the paper web. In our copending application U.S. Ser. No. 304,106 led August 23, 1963, now U.S. Patent No. 3,204,552 we have provided mechanism for controlling the weight of bearings of a calender stack and loading the calender stack nips by applying the forces to the top roll.

It is an object of the present invention to provide an improved calender stack structure wherein increased capacity and improved results can be achieved by operating each of the nips at optimum pressure and in accordance with the mechanism method of the present invention the pressure in the nips is controlled so that each nip operates at substantially the same pressure which is chosen to be the optimum working pressure for the particular sheet being calendered.

A further object of the invention is to provide au improved device wherein improved calendered paper results because of stabilizing in the nips and the reduction of vibration so as to avoid barring and other defects that result in calenders wherein the operation Iof the individual rolls is not stabilized.

Other objects, advantages and features will become more apparent with the teaching of the principles of the present invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings, in which:

FIGURE 1 is a schematic elevational view of a calender stack embodying the principles of the present invention;

FIGURE 2 is a fragmentary schematic view similar to FIGURE 1 and showing a modification of the invention;

FIGURE 3 is a fragmentary view of a calender stack, similar to FIGURE 1, and showing a modification of the arrangement; and

FIGURE 4 is a graph showing nip pressures in calender stacks of the type heretofore available and in a calender stack embodying the principles of the present invention.

On the drawings:

In the arrangement of FIGURE 1 a calender stack is shown having a lower king roll 10 with intermediate rolls 11, 12 and 13. A top roll 14 is at the top of the stack and nips 15, 16, 17 and 18 are provided between the vertical arranged horizontally disposed rolls with 15 being the lowermost nip and 1S the uppermost nip.

lEach of the rolls are provided with journals supported in bearings shown schematically at the ends of the rolls.

The lowermost king roll 10 is provided with a heavy bearing in the conventional calender stack to support the weight of the king roil 10` and the rolls thereabove. In the present arrangement the bearing for the lower king roll does not have to support the remainder of the stack in operation, but merely has to carry the Weight of the king roll 10 plus the nip forces due to loading of the top roll. The lowermost bearing for the king roll is supported by first forces 19 and 20, and roll deflection control forces 21 and 22 may be applied to obtain a substantially uniform nip pressure along the ni-p 14. This may be obtained by crowning the king roll in a manner such as illustrated in Patent 2,850,952, Hornbostel, or by deection control means such as illustrated in Patent 3,060,843, Moore et al.

For loading the stack, loading forces 23 are applied to the top roll 14. These forces are in an amount so that a nip load will be reached in the nip 18 equal to the 3 optimum or maximum nip load which in a predetermined desired loadcan be tolerated by the paper sheet. In the usual calender construction the top roll is loaded until the load in the lowermost nip reaches the maximum tolerable load. This is not the case in the present arrangement, and in accordance with the present structure and method the top roll 14 is loaded by the loading forces 23 until maximum tolerable nip load is reached in the nip 118.

Under usual conditions, each of the successive nips below the top nip, namely 17, 16 and 15 will be increased due to the weight of the intermediate rolls 13, 12 and 11. In a typical paper machine the diameter of the intermediate rolls will be about 18 inches and will have an axial dimension which is the width of the paper machine which can be on the order of 20 to 25 feet or more. Thus the intermediate rolls have a substantial weight and the bottom ni-p 15 will be loaded by the loading of the top roll plus the weight of each of the intermediate rolls. In accordance with the method of the present invention each of the intermediate rolls is supported with a force equal to its total weight, that is the weight of the roll plus its bearings so that it is substantially floating or weightless. We have discovered that this arrangement effects a substantial advantage in stability of the overall stack. A significant problem in the operation of calender rolls is chattering or vibration which causes barring and damage to the paper web and the cause for this arrangement is not fully known. However, by reducing the weight of each of the intermediate rolls to an amount where it is substantially weightless this vibration has been all but eliminated.

Upward forces are applied as indicated schematically at 24 and 25, to the intermediate roll 13, in an amount equal to the weight -of the roll 13 and its bearings. Similarly upward forces 26 and 27 are applied to the roll 12 equal to its weight in the weight of its bearings. Also, upward forces 28 and 29 are applied to the roll 11 equal to the weight of the roll and its bearings. These forces are applied in a convenient manner and as shown schematically may be obtained by applying an upward force directly to the bearing. Mechanism for accomplishing this is illustrated in our copending application Ser. No. 304,- 106 although the size of the lifting bellows shown therein has to be increased so as to be capable of lifting not only the bearings but also the roll weight.

FIGURE 2 illustrates another maner in which the top roll can be loaded. The top load 14' is shown above intermediate rolls 13' and 12' and has conventional end bearings which are loaded by forces shown schematically at 30 and 31. This end loading will tend to cause nonuniform loading along the nip due to bending of the top roll 14'. To compensate for this deflection, control means are provided such as by applying roll bending forces 32 and 33 axially outwardly of the loading forces 30 and 31. A structure which may be used to accomplish this is illustrated in the U.S. Patent 3,060,843 Moore et al.

While the utilization of the forces on the intermediate roll to cause weightlessness does usually not bend the rolls sufficiently to cause a high degree of non-uniform nip pressure, in some instances it is desirable to apply deflection control forces to the intermediate rolls. This is illustrated in FIGURE` 3 wherein the top roll is shown at 14" and intermediate rolls are shown at 13" and 12". Lifting forces 34 and 35 are applied to the intermediate roll 13 and lifting forces 38 and 39 are applied to the intermediate roll 12". In addition deflection control forces 36 and 37 are applied to the intermediate roll 13" and deflection control forces 40 and 41 are applied to the intermediate roll 12". The deflection control forces combined with the roll lifting forces must be such that their net resultant `force is equal to the Weight of the intermediate roll plus its bearings.

It will -be understood that while deflection control devices are shown applying a couple to the bearings at the 4 ends of the rolls, other deflection control devices may .be employed.

FIGURE 4 illustrates the relationship between the nip loads of different nips in a conventional calender stack, and a calender stack operated and constructed in accordance with the principles of the present invention.

The line NL-l shows a conventional calender stack wherein the nip load is such that the pressure in the lowermost nip N-1 exceeds the maximum tolerable pressure of the web beingtreated, and reaches the damage pressure. In order to reduce the load in the lowermost nip to a safe operating pressure it is necessary that the load be relieved on the'` top roll so that the nips have a loading shown by the broken line. NL-Z. This of course substantially Areduces the calendering effect on the web from the top roll which has the nip N-15 below it and the top roll actually has to be lifted in some cases to avoid an excess pressure in the lowermost nip. In any event the pressure in the upper nip's is so low that useful calendering cannot be accomplished.

With the present arrangement the nip loading indicated by the solid line NL-3 is achieved. Each of the nips will be operated at the maximum pressure. This will result in the most useful nip load in each of the nips. This will also make possible a reduction in the number of rolls necessary in a calender stack and increase the capacity of any stack with a given number of rolls.

It will be understood that the invention may be employed with the arrangements of FIGURES 1, 2 and 3 or any combinations of arrangements. For example, the deflection control arrangements for the intermediate rolls illustrated in FIGURE 3 may be used with any form of top roll loading such as shown in FIGURES 1 or 2.

Thus it will be seen that we have provided an improved method and structure for calendering, which meets the objectives and features above set forth. An improved paper web results in that vibration dampening is achieved and increased calender capacity is obtained.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

We claim as our invention:

1. The method of calendering a web of paper in a vertical calender stack having a lower king roll, a top roll and intermediate rolls which comprises:

controlling the deflection of the king roll to obtain a uniform load alongr the length of its nip,

`applying a predetermined vertical loading force to the top roll in an amount obtaining a predetermined nip load in the top nip,

and applying vertical lifting forces to each of the intermediate rolls equal to the weight of their respective rolls and bearings so that said predetermined nip load will exist in each nip in the stack.

2. The method of calendering a web of paper in a vertical calender stack having -a lower king roll, a top roll and intermediate rolls which comprises:

controlling the deflection of the king roll to obtain a uniform load along the length of its nip, applying a predetermined vertical loading force to the top roll in an amount obtaining a predetermined nip load in the top nip,

controlling the deflection of the top roll for obtaining a uniform nip load along its length, and applying vertical lifting forces to each of the intermediate rolls equal to the weight of their respective rolls and ybearings so that said predetermined nip load will exist in each nip in the stack.

3. The method of calendering a web of paper in a vertical calender stack having a lower king roll, a top roll and intermediate rolls each having end bearings, which comprises:

controlling the deflection of the king roll to obtain a uniform load along the length of its nip,

applying a predetermined vertical loading force to the top roll in an amount obtaining -a predetermined nip load in the top nip,

and applying a lifting force to the bearings of each intermediate roll equal to the Weight of its roll and `bearings so that said predetermined nip load will exist in each nip in the stack.

4l., The method of calendering ya web of paper in a vertical calender stack having a lower king roll, a top roll and intermediate rolls each having end bearings, which comprises:

controlling the deflection of the king roll to obtain a uniform load along the length of its nip,

applying -a predetermined vertical loading force to the end bearings of the top roll in an amount to obtain a predetermined nip load in the top nip,

controlling the deection of the top roll to obtain a uniform nip load along its length,

and applying vertical lifting forces to the end bearings of each of the intermediate rolls in an amount equal to the weight of their bearings and the roll so that said predetermined nip load will exist in each nip in the stack.

5. The method of calendering a web of paper in a vertical calender stack having -a lower king roll, a top roll and intermediate rolls which comprises:

applying a predetermined vertical loading force to the top roll in an amount obtaining a predetermined nip load in the top nip,

applying vertical lifting forces to each of the intermediate rolls equal to the weight of their respective rolls and bearings so that said predetermined nip load will exist in each nip in the stack, and

controlling the deection of the intermediate roll so that uniform nip load will be obtained along each of the nips.

6. The method of calendering a web of paper in a vertical calender ystack having a lower king roll, a top roll and intermediate rolls which comprises:

applying a predetermined vertical loading force to the top roll in an amount obtaining a predetermined nip load in the top nip,

and applying vertical lifting forces to each of the intermediate rolls equal to the weight of their respective rolls and bearings 'so that said predetermined nip load will exist in each nip in the stack.

References Cited UNITED STATES PATENTS 2,850,952 9/1958 Hornbostel 100--163 2,985,100 5/1961 Hornbostel 100-163 3,044,440 7/1962 Molsberry et al. 100-170 X 3,060,843 l0/l962 Moore et al 100-170 X 3,155,029 11/1964 Thomas 100-170 3,157,110 11/1964 Goddard 100-170 3,158,088 11/1964 Seidel 100-163 FOREIGN PATENTS 440,634 l/ 1936 Great Britain.

794,581 12/ 1935 France. 1,054,953 4/ 1959 Germany.

LOUIS O. MAASSEL, Primary Examiner. 

